The present invention relates to a method and apparatus for adjusting an ink supply amount for a multicolor printing press, which adjust the amount of ink to be supplied to a plate by adjusting setting of the opening amount of an ink fountain key and the feed rate (rotation amount) of an ink fountain roller.
A four-color rotary printing press shown in FIG. 18 has printing units 9-1 to 9-4 provided for four ink colors. An ink supply unit shown in FIG. 17 is provided in each of the printing units 9-1 to 9-4.
The ink supply unit shown in FIG. 17 has an ink fountain 1, an ink 2 stored in the ink fountain 1, an ink fountain roller 3, a plurality of ink fountain keys 4 (4-1 to 4-n) aligned in the axial direction of the ink fountain roller 3, an ink ductor roller 5, an ink roller group 6, a plate 7, and a plate cylinder 8.
In the printing press having the above arrangement, the amount of ink to be supplied from the ink fountain 1 to the ink fountain roller 3 is adjusted by adjusting the opening amounts of the ink fountain keys 4. The amount of ink to be supplied from the ink fountain roller 3 to the plate 7 through the ink roller group 6 is adjusted by adjusting the feed rate (rotation amount) of the ink fountain roller 3. A print sheet is printed with the ink finally supplied to the plate 7.
The opening amount of each ink fountain key 4 is set in accordance with the image area ratio of each of areas, corresponding to the ink fountain keys 4, of the plate 7 by following the xe2x80x9cconversion curve of the image area ratio to the opening amount of the ink fountain keyxe2x80x9d stored in advance. The feed rate of the ink fountain roller 3 is set in accordance with a predetermined reference ink feed rate. The opening amounts of the ink fountain keys 4 and the feed rate of the ink fountain roller 3 (ink feed rate) are set in units of printing units 9-1 to 9-4. More specifically, the xe2x80x9cconversion curve of the image area ratio to the opening amount of the ink fountain keyxe2x80x9d and the reference ink feed rate are determined in units of ink colors.
Conventionally, since the xe2x80x9cconversion curve of the image area ratio to the opening amount of the ink fountain keyxe2x80x9d and the reference ink feed rate are uniquely determined by the printing machine manufacturer, differences in standard density among the printing companies and differences depending on the environment are not considered. For this reason, the operator of each printing company actually checks the color of the printed printing product after the opening amounts of the respective ink fountain keys 4 and the feed rate of the ink fountain roller 3 are set by using the standard characteristics in units of printing units 9-1 to 9-4.
In accordance with the result of color checking, the operator finely adjusts the opening amounts of the ink fountain keys 4 separately, or the feed rate of the ink fountain roller 3, thereby dealing with the differences in standard density and the differences depending on the environment. This fine adjustment of the amount of ink to be supplied requires a very advanced technique and can be performed only by a skilled operator. The fine adjustment takes a very long period of time, leading to a delay in printing operation.
Also, conventionally, the xe2x80x9cconversion curve of the image area ratio to the opening amount of the ink fountain keyxe2x80x9d and the reference ink feed rate must be stored in units of ink colors, and a very large memory capacity is accordingly necessary.
It is an object of the present invention to provide a method and apparatus for adjusting an ink supply amount for a multicolor printing press, which can perform color matching for actual printing and set and adjust the amount of ink to be supplied easily and within a short period of time.
It is another object of the present invention to provide a method and apparatus for adjusting an ink supply amount for a multicolor printing press, which do not require a very large memory capacity.
In order to achieve the above objects, according to the present invention, there is provided an ink supply amount adjusting method for a multicolor printing press which performs multicolor printing with a plurality of printing units provided to correspond to a plurality of ink colors, each of the printing units having an ink fountain for storing an ink, an ink fountain roller to which the ink is supplied from the ink fountain, a plurality of ink fountain keys aligned in an axial direction of the ink fountain roller to adjust an amount of ink to be supplied from the ink fountain to the ink fountain roller, and an ink roller group for supplying the ink to a plate in an amount adjusted in accordance with a feed rate of the ink fountain roller, comprising the steps of
obtaining reference opening amounts of the ink fountain keys in units of ink colors in accordance with image area ratios of respective areas, corresponding to the ink fountain keys, of the plate by following a relationship between an image area ratio and opening amounts of the ink fountain keys, the relationship being preset to be common to the respective ink colors, and
uniformly correcting the obtained reference opening amounts of the ink fountain keys in units of ink colors with correction values preset in units of ink colors, thereby obtaining set values of the opening amounts of the ink fountain keys in units of ink colors.